System and method for estimating number and range of a plurality of moving targets

Abstract

System and method for estimating locations and range rates of a multiplicity of targets by estimating range-Doppler state representation, including: computing a prior range-Doppler state estimate matrix and a measurement matrix containing phase shifted and re-ordered samples of a transmitted signal waveform; applying the measurement matrix to the range-Doppler state estimate matrix to generate a prediction of a current return sample and calculating a difference between the current return signal sample and the prediction of the current return signal sample; multiplying the difference by a gain matrix to obtain an adjustment to the prior range-Doppler state estimate matrix; repeating the process for a next return signal; computing an estimated range-Doppler map (RDM); applying a threshold to the estimated RDM to detect individual targets and obtain their range and Doppler parameters; and using the range and Doppler parameters to estimate the locations and range rates of the targets.

What is claimed is: 
     
       1. A method for estimating locations and range rates of a multiplicity of targets by estimating range-Doppler state representation, the method comprising:
 a. transmitting an arbitrary signal waveform by a transmitter; 
 b. receiving a plurality of return signal samples reflected from the targets, by a receiver; 
 c. computing and initializing a prior range-Doppler state estimate matrix, wherein the range-Doppler state estimate matrix is a two-dimensional matrix with a first index corresponding to a range and a second index corresponding to Doppler frequency of each potentially detected target; 
 d. computing a measurement matrix containing phase shifted and re-ordered samples of the transmitted signal waveform; wherein computing the measurement matrix depends only on the transmitted signal and is independent of the return signal samples. 
 e. applying the measurement matrix to the prior range-Doppler state estimate matrix to generate a prediction of a current return sample, and calculating a difference between the current return signal sample and the prediction of the current return signal sample; 
 f. multiplying the difference by a gain matrix to obtain an adjustment to the prior state estimate matrix, wherein the gain matrix includes values that are re-calculated for each return signal sample; 
 g. adding the adjustment to the prior range-Doppler state estimate matrix to obtain an updated range-Doppler state estimate matrix; 
 h. repeating steps d to g for a next return signal sample using the updated state estimate matrix as the prior state estimate matrix for said next return signal sample, for a predetermined number of times to generate a final state estimate matrix; 
 i. taking magnitudes of the elements of the final state estimate matrix to compute an estimated range-Doppler map (RDM); 
 j. applying a threshold to the estimated RDM to detect individual targets and obtain their range and Doppler parameters; and 
 k. using the range and Doppler parameters to estimate the locations and range rates of the targets. 
 
     
     
       2. The method of  claim 1 , wherein computing the estimated RDM further comprises taking the magnitudes of each of complex valued elements of the final state estimate matrix. 
     
     
       3. The method of  claim 1 , wherein each element of the RDM is the sum of the squares of the real and imaginary parts of the corresponding element of the final state estimate matrix and represents estimates of the amplitudes of the multiplicity of targets with corresponding range and Doppler. 
     
     
       4. The method of  claim 3 , wherein a presence of a target is indicated by values in RDM elements corresponding to the range and Doppler of the targets that are larger than a predetermined threshold. 
     
     
       5. The method of  claim 1 , wherein the estimated locations and range rates of the targets is utilized for one or more of navigating around or to the targets, monitoring speed of the targets, tracking one or more of the targets, forecasting the weather, locking a radar to one or more of the targets, directing a camera or a weapon towards one or more of the targets, and recognizing one or more of the targets. 
     
     
       6. The method of  claim 1 , wherein gain matrix values are independent of the return signal sample values. 
     
     
       7. The method of  claim 1 , further comprising displaying the estimated RDM on a display screen as an image, with brightness or color contrasts corresponding to the amplitude of each range-Doppler value. 
     
     
       8. A radar system for estimating locations and range rates of a multiplicity of targets by estimating range-Doppler state representation comprising:
 a transmitter for transmitting an arbitrary signal waveform; 
 a receiver for receiving a plurality of return signal samples reflected from the targets; and 
 a processor including a memory for
 a. computing and initializing a prior range-Doppler state estimate matrix, wherein the range-Doppler state estimate matrix is a two-dimensional matrix with a first index corresponding to a range and a second index corresponding to Doppler frequency of each potentially detected target; 
 b. computing a measurement matrix containing phase shifted and re-ordered samples of the transmitted signal waveform; wherein computing the measurement matrix depends only on the transmitted signal and is independent of the return signal samples. 
 c. applying the measurement matrix to the prior range-Doppler state estimate matrix to generate a prediction of a current return sample, and calculating a difference between the current return signal sample and the prediction of the current return signal sample; 
 e. multiplying the difference by a gain matrix to obtain an adjustment to the prior state estimate matrix, wherein the gain matrix includes values that are re-calculated for each return signal sample; 
 f. adding the adjustment to the prior range-Doppler state estimate matrix to obtain an updated range-Doppler state estimate matrix; 
 g. repeating processes b to f for a next return signal sample using the updated state estimate matrix as the prior state estimate matrix for said next return signal sample, for a predetermined number of times to generate a final state estimate matrix; 
 h. taking magnitudes of the elements of the final state estimate matrix to compute an estimated range-Doppler map (RDM); 
 i. applying a threshold to the estimated RDM to detect individual targets and obtain their range and Doppler parameters; and 
 j. using the range and Doppler parameters to estimate locations and range rates of the targets. 
 
 
     
     
       9. The radar system of  claim 8 , wherein the processor takes the magnitudes of each of complex valued elements of the final state estimate matrix to compute the estimated RDM. 
     
     
       10. The radar system of  claim 8 , wherein each element of the RDM is the sum of the squares of the real and imaginary parts of the corresponding element of the final state estimate matrix and represents estimates of the amplitudes of the multiplicity of targets with corresponding range and Doppler. 
     
     
       11. The radar system of  claim 10 , wherein a presence of a target is indicated by values in RDM elements corresponding to the range and Doppler of the targets that are larger than a predetermined threshold. 
     
     
       12. The radar system of  claim 8 , wherein the estimated locations and range rates of the targets is utilized for one or more of navigating around or to the targets, monitoring speed of the targets, tracking one or more of the targets, forecasting the weather, locking a radar to one or more of the targets, directing a camera or a weapon towards one or more of the targets, and recognizing one or more of the targets. 
     
     
       13. The radar system of  claim 8 , wherein gain matrix values are independent of the return signal sample values. 
     
     
       14. The radar system of  claim 8 , further comprising a display screen for displaying the estimated RDM as an image, with brightness or color contrasts corresponding to the amplitude of each range-Doppler value.